Optimized monolithic 2-D spin-valve sensor for high-sensitivity compass applications
We have designed and fabricated 2-D giant magnetoresistance spin-valve sensors on the basis of exchange-biased NiFe-CoFe/Cu/CoFe/IrMn nanolayers in monolithic integration for high-sensitivity compass applications. For a maximum signal-to-noise ratio, we have realized a focused double full-bridge layout with an antiparallel alignment of the pinned layer magnetization for neighboring meanders. This precise alignment is achieved with microscopic resolution by laser heating and subsequent in-field cooling. Striving for high-signal sensitivity and low hysteresis, we study in detail how the geometry of the constituent single meanders influences their magnetic structure and the resulting electronic transport properties. The investigated geometrical parameters include stripe width, stripe length, U-turn material, and total meander length. Moreover, the influence of the relative alignment between reference magnetization and shape anisotropy is studied. We compare our experimental results to the predictions of tailored micromagnetic simulations. Applying the best-suited meander geometry, we demonstrate how the developed 2-D sensor may be readily employed to determine the direction of small magnetic fields, such as that of the Earth, as a 2-D vector with high spatial (~1mm) and temporal (~1ms) resolution.